The invention relates to a heating or air-conditioning ventilation unit having a radial blower. The unit can be used, for example, in motor vehicles.
Heating or air-conditioning units of this type are known. In passenger motor vehicles in particular, only a limited construction space is available for the heating or air-conditioning unit, so that the diffuser of the radial blower has to be kept as short as possible, However, since the end face of the heat exchanger connected on the outlet side of the blower is considerably larger than the discharge cross-section of the blower, extreme spreading of the flow over a short distance is necessary. This applies not only with regard to the radial widening of the spiral in the radial blower, but also with regard to the axial widening in the diffuser.
Because of the large opening angle of the diffuser and the extreme cross-sectional widening connected therewith, air is admitted to the heat exchanger non-uniformly, with less air flowing through the edge areas of the heat exchanger than the center part. Moreover, return flows form in the diffuser which, apart from the above-mentioned non-uniform admission to the heat exchanger, lead to efficiency losses and to increased noise generation.